I've cut my animal protein consumption at least 50% in the last 10 years and am in noticeably better condition than when eating average levels of meat. I now consider myself vegetarian as I get most of my protein from eggs, dairy and fish, with small amounts of red meat occasionally.

I suppose it's the fact meat makes the blood acidic, which has to be buffered by critical minerals robbed from various organs and muscles. It also requires much "energy" to digest which has to be diverted from other critical body functions. I don't go full vegan because I do believe in balance, but do credit the move away from heavy meat consumption for much improved overall health, while noticing other people my age falling prey to various ills.